Electronics > Projects, Designs, and Technical Stuff
Bench CC/CV PSU Based on Daves uSupply (Not Anymore)
KC0PPH:
Ill post the schematic and layout later tonight.
Once again thanks for all the input. I have made some significant changes to the board due to size creep. I am hoping to keep the board to the size that it currently is.
As for schematic changes. I added R33 and R34 to IC1C (OA Powering CC LED) as it was suggested that connecting the inputs together was a bad idea.
I added 2 resistors to the Voltage REF. I set the Lower one to 50K and the upper one to 0R so I should still get the 2.5V output (I need to verify on the datasheet).
I also changed the OA power source to be on the other side of the 10 ohm resistors as it was suggested to do that for isolation and filtering.
Q4 Will be changing to a larger SMD device. I need to google some good alternatives.
So a few questions:
1) Is my V_SENSE voltage divider correct? If not where did I go wrong?
2) Is my resistor networks for IC1B Correct? I believe I should get 0-5 on inverting input (Based on 0-15Vout). I am guessing I need a 0-1V signal on I_SET for 0-1A but I am pretty sure I am wrong.
3) Are my Pots Correct? Assuming I want a 0-5V and 0-1V on the wipers.
I Will post the schematic later tonight, although none of the values I am talking about in points 1-3 have changed.
KC0PPH:
Here are the files.
not1xor1:
--- Quote from: jaycee on March 25, 2019, 11:24:42 am ---edit: AS others have said about the current limit LED, you can simply connect the cathode of the LED to I_SENSE and use a suitable limiting resistor. When the current limit is not in operation, the output of the opamp will be close to the +V rail, and the LED wont light. When it is operating, it will be somewhere near the -V rail and thus the led will light.
--- End quote ---
IMHO this is much simpler and provides both CV and CC monitoring.
Notice that the opamp are ... criss-crossed as the voltage regulation opamp drives the CC LED and vice-versa.
It is a sort of OFF indication and since either of those 2 opamps has to be ON... :)
iMo:
The TL431 has to be wired this way when used as a Vref:
iMo:
--- Quote from: KC0PPH on March 26, 2019, 12:45:07 am ---..So a few questions:
1) Is my V_SENSE voltage divider correct? If not where did I go wrong?
2) Is my resistor networks for IC1B Correct? I believe I should get 0-5 on inverting input (Based on 0-15Vout). I am guessing I need a 0-1V signal on I_SET for 0-1A but I am pretty sure I am wrong.
3) Are my Pots Correct? Assuming I want a 0-5V and 0-1V on the wipers.
--- End quote ---
Your resistor's values:
The Vout will be the voltage on the Vset pot's wiper multiplied by the divider's ratio, in your case 51k/25k=3.04, therefore Vout = 3.04 x Vset.
The SLowCC will be set to 1A with 1V on the Iset pot's wiper when all 4 resistors around the Isense opamp IC1B will have the same value AND the Rshunt will be 1ohm.
Note: above is valid when the 560k resistors are not populated.
The pots and resistors in series with them look ok.
Because of the 560k resistors there will be a small nonlinearity in the pot's scales.
Also the Iset's pot wiper voltage will be influenced by the network around the Isense opamp.
PS: the I_set's setting looks to be an issue >:D
The setting is heavily influenced by the resistor's values in the Isense IC1B diff amplifier and the Vout.
The I_set has to be either
a) pretty low impedance, or
b) the resistors around IC1B have to be pretty large values.
It seems you need to buffer the I_set.
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